During the first years support of this project we showed that adenosine has to be metabolized in order to support the rabbit corneal endothelial pump. We also showed that deamination is the probable metabolic pathway. In the second year of support we shall study the involvement of purine and pyrimidine metabolism in relation to the activity of the corneal endothelial pump. This will be done by perfusing with the intermediates and inhibitors of the nucleoside metabolism.